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3/ Chu vi hình chữ nhật:
\(\left(\dfrac{1}{4}+\dfrac{3}{10}\right)\cdot2=\dfrac{11}{10}\) (chưa biết đơn vị)
Diện tích hình chữ nhật:
\(\dfrac{1}{4}\cdot\dfrac{3}{10}=\dfrac{11}{20}\) (chưa biết đơn vị)
\(1,3.\dfrac{15}{39}-\left(\dfrac{4}{5}+\dfrac{2}{3}\right):2\dfrac{1}{5}\)
\(=\dfrac{13}{10}.\dfrac{15}{39}-\dfrac{22}{15}:\dfrac{11}{5}\)
\(=\dfrac{1}{2}-\dfrac{2}{3}=-\dfrac{1}{6}\)
\(10A=\dfrac{10^{12}-10}{10^{12}-1}=1-\dfrac{9}{10^{12}-1}\)
\(10B=\dfrac{10^{11}+10}{10^{11}+1}=1+\dfrac{9}{10^{11}+1}\)
Vì \(10^{12}-1>10^{11}+1\)
nên \(-\dfrac{9}{10^{12}-1}>-\dfrac{9}{10^{11}+1}\)
hay A>B
\(\left(\dfrac{2}{3}+x\right)\left(\dfrac{3}{5}-2x\right)=10\)
\(\Leftrightarrow\dfrac{2}{3}+x;\dfrac{3}{5}-2x\inƯ\left(10\right)\)
\(Ư\left(10\right)=\left\{\pm1;\pm2;\pm5;\pm10\right\}\)
\(\Leftrightarrow\dfrac{2}{3}+x=1\Rightarrow x=\dfrac{1}{3}\)
\(\dfrac{3}{5}-2x=10\Rightarrow2x=\dfrac{-47}{5}\Rightarrow x=\dfrac{-47}{10}\)
\(\Leftrightarrow\dfrac{2}{3}+x=-1\Rightarrow x=\dfrac{-5}{3}\)
\(\dfrac{3}{5}-2x=-10\Rightarrow2x=\dfrac{53}{5}\Rightarrow x=\dfrac{53}{10}\)
\(\Leftrightarrow\dfrac{2}{3}+x=2\Rightarrow x=\dfrac{4}{3}\)
\(\dfrac{3}{5}-2x=5\Rightarrow2x=\dfrac{-22}{5}\Rightarrow x=\dfrac{-11}{5}\)
\(\Leftrightarrow\dfrac{2}{3}+x=-2\Rightarrow x=\dfrac{-8}{3}\)
\(\dfrac{3}{5}-2x=-5\Rightarrow2x=\dfrac{28}{5}\Rightarrow x=\dfrac{14}{5}\)
\(\Leftrightarrow\dfrac{2}{3}+x=5\Rightarrow x=\dfrac{13}{3}\)
\(\dfrac{3}{5}-2x=2\Rightarrow2x=\dfrac{-7}{5}\Rightarrow x=\dfrac{-7}{10}\)
\(\Leftrightarrow\dfrac{2}{3}+x=-5\Rightarrow x=\dfrac{-17}{3}\)
\(\dfrac{3}{5}-2x=-2\Rightarrow2x=\dfrac{13}{5}\Rightarrow x=\dfrac{13}{10}\)
\(\Leftrightarrow\dfrac{2}{3}+x=10\Rightarrow x=\dfrac{28}{3}\)
\(\dfrac{3}{5}-2x=1\Rightarrow2x=\dfrac{-2}{5}\Rightarrow x=\dfrac{-1}{5}\)
\(\Leftrightarrow\dfrac{2}{3}+x=-10\Rightarrow x=\dfrac{-32}{3}\)
\(\dfrac{3}{5}-2x=-1\Rightarrow2x=\dfrac{8}{5}\Rightarrow x=\dfrac{4}{5}\)
Mk hơi băn khoăn chỗ này . Tại sao mà trong 1 trường hợp mà x lại khác nhau ?
1,=0 . [2017/2018+2018/2019]
=>0
2,TH1 x-3=0=>x=3
TH2 y-4=0=>y=4
3, -2/4 = -x/10 = 16/y
=>-1/2 = -x/10 = 16/y
=>-1/2 = -x/10 => -5/10 = -x/10 => x=5
-1/2 = 16/y => 16/-32 = 16/y => y = -32
a, \(x+\dfrac{2}{3}=0,2\)
\(\Rightarrow x+\dfrac{2}{3}=\dfrac{1}{5}\)
\(\Rightarrow x=\dfrac{1}{5}-\dfrac{2}{3}\)
\(\Rightarrow x=\dfrac{-7}{10}\)
b, \(\dfrac{17}{7}-\dfrac{6}{5}x=\dfrac{17}{4}\)
\(\Rightarrow\dfrac{6}{5}x=\dfrac{17}{7}-\dfrac{17}{4}\)
\(\Rightarrow\dfrac{6}{5}x=\dfrac{-51}{28}\)
\(\Rightarrow x=\dfrac{-51}{28}:\dfrac{6}{5}\)
\(\Rightarrow x=\dfrac{-85}{56}\)
\(a)\) \(x+\dfrac{2}{3}=0,2\)
\(\Rightarrow x+\dfrac{2}{3}=\dfrac{1}{5}\)
\(\Rightarrow x=-\dfrac{7}{15}\)
Vậy ...
\(b)\) \(\dfrac{17}{7}-\dfrac{6}{5}x=\dfrac{17}{4}\)
\(\Rightarrow\dfrac{6}{5}x=\dfrac{-51}{28}\)
\(\Rightarrow x=-\dfrac{85}{56}\)
Vậy ...
\(x=0,2-\dfrac{2}{3}\)
\(x=-\dfrac{7}{15}\)
\(-\dfrac{6}{5}x=\dfrac{17}{4}-\dfrac{17}{7}\)
\(-\dfrac{6}{5}x=\dfrac{51}{28}\)
\(x=\dfrac{51}{28}:\left(\dfrac{-6}{5}\right)\)
\(x=\dfrac{-85}{56}\)
\(x+\dfrac{2}{3}=0,2\left(a\right)\\ \Rightarrow x=0,2-\dfrac{2}{3}\\\Rightarrow x=\dfrac{1}{5}-\dfrac{2}{3}\\ \Rightarrow x=\dfrac{3}{15}-\dfrac{10}{15}\\ \Rightarrow x=-\dfrac{7}{15} \)
Vậy tập nghiệm phương trình (a) là \(\left\{-\dfrac{7}{15}\right\}\).
--------------------
\(\dfrac{17}{7}-\dfrac{6}{5}\cdot x=\dfrac{17}{4}\left(b\right)\\ \Leftrightarrow\dfrac{6}{5}x=\dfrac{17}{4}-\dfrac{17}{7}\\ \Leftrightarrow\dfrac{6}{5}x=\dfrac{119}{28}-\dfrac{68}{28}\\ \Leftrightarrow\dfrac{6}{5}x=\dfrac{51}{28}\\ \Rightarrow x=\dfrac{51}{28}:\dfrac{6}{5}\\ \Rightarrow x=\dfrac{51}{28}\cdot\dfrac{5}{6}\\ \Rightarrow x=\dfrac{255}{168}\\ \Rightarrow x=\dfrac{85}{56}\)
Vậy tập nghiệm phương trình (b) là \(\left\{\dfrac{85}{56}\right\}\).
\(x+\dfrac{2}{3}=0,2\)
x + \(\dfrac{2}{3}=\dfrac{1}{5}\)
x = \(\dfrac{1}{5}-\dfrac{2}{3}\)
x = \(\dfrac{3}{15}-\dfrac{10}{15}\)
\(x=\dfrac{3+\left(-10\right)}{15}\)
x = \(\dfrac{-7}{15}\)
Vậy x = \(\dfrac{-7}{15}\)
\(\dfrac{17}{7}-\dfrac{6}{5}.x=\dfrac{17}{4}\)
\(\dfrac{6}{5}.x=\dfrac{17}{7}-\dfrac{17}{4}\)
\(\dfrac{6}{5}.x=\dfrac{-51}{28}\)
\(x=\dfrac{-51}{28}:\dfrac{6}{5}\)
\(x=\dfrac{-51}{28}.\dfrac{5}{6}\)
\(x=\dfrac{-85}{56}\)
Vậy x = \(\dfrac{-85}{56}\)
.-. Tự nhiên cho cái nghiệm vào, lớp 6 đâu đã học.
Nguyễn Xuân Sáng Lớp 7 cũng chưa cần, nhưng thêm vào để cho quen, lên lớp 8 đỡ quên :)
Tuấn Anh Phan Nguyễn uhm ^^